The present invention relates to an exposure apparatus and exposure method, and a device and its manufacturing method. More particularly, the present invention relates to an exposure apparatus used to manufacture semiconductor devices and liquid crystal display devices and the like in a lithographic process and the exposure method, and a device manufactured by using the exposure apparatus and its manufacturing method using the exposure method to manufacture the device.
Conventionally, in a lithographic process which is a process when manufacturing a semiconductor device, various exposure apparatus are used to transfer a circuit pattern formed on a mask or a reticle (hereinafter referred to as a xe2x80x9creticlexe2x80x9d in general) onto a substrate such as a wafer or a glass plate and the like that are coated with a resist (photoresist).
For example, with the exposure apparatus for semiconductor devices, the reduction projection exposure apparatus that reduces and transfers the pattern formed on a reticle using a projection optical system is mainly used, so as to comply with the finer minimum line width (device rule) of the pattern required with the higher integration of the integrated circuits.
Of the reduction projection exposure apparatus, the static type exposure apparatus (the so-called stepper) which employs the step-and-repeat method to sequentially transfer the pattern formed on the reticle to a plurality of shot areas on the wafer, or an improvement of the stepper which is the scanning exposure apparatus that employs the step-and-scan method (the so-called scanning stepper) disclosed in, for example, Japanese Patent Laid Open No. 08-166043, which synchronously moves the reticle and the wafer in a one dimensional direction and transfers the reticle pattern onto each shot area on the wafer, are well known.
With these reduction projection exposure apparatus, a base plate which is to be the base of the apparatus, is first of all, arranged on the floor. And on the base plate, the main column which supports the reticle stage, the wafer stage, and the projection optical system (projection lens) and the like, is mounted via the vibration isolator which is arranged to isolate the vibration travelling through the floor. With recent reduction projection exposure apparatus, as the vibration isolator, an active vibration isolator is employed. The active vibration isolator comprises an air mount which the internal pressure is adjustable and a voice coil motor, and the vibration of the main column is suppressed by controlling the voice coil motor and the like based on the measurement values of the six accelerometers attached to the main column (mainframe).
With the steppers, after a shot area on the wafer is exposed, exposure is sequentially repeated onto the remaining shot areas. Therefore, the reaction force due to the acceleration and deceleration of the wafer stage (in the case of the stepper) or the reticle stage and the wafer stage (in the case of the scanning stepper) was the cause of vibration of the main column, which in turn caused an unfavorable situation such as creating a positional relationship error between the projection optical system and the wafer.
The error in the positional relationship on alignment and on exposure has consequently been the cause of the pattern being transferred onto a position on the wafer different from the designed value, or in the case the positional error includes a vibration component, led to an image blur (increase in the pattern line width).
Accordingly, in order to prevent the pattern being transferred from shifting, or to suppress the image blur, the vibration of the main column needed to be sufficiently attenuated, such as by the active vibration isolator described above. For example, in the case of the stepper, alignment operation and exposure operation was to begin after the wafer stage was positioned at the desired place and has sufficiently settled down, whereas in the case of the scanning stepper, the reticle stage and the wafer stage had to be sufficiently settled in synchronous before exposure was performed. Consequently, these were causes of lowering the throughput (productivity).
With the size of the wafer increasing in recent years, the size of the wafer stage has also increased, making it difficult to secure the throughput to some extent and performing precise exposure even by using the active vibration isolator earlier described.
To solve such inconvenience, in the Japanese Patent Laid Open No. 02-199813, an exposure apparatus is proposed, which stage holding the substrate and the projection lens mount holding the projection lens are arranged on separate vibration isolation mounts.
However, to arrange the vibration isolation mount on the floor is difficult, due to the features of the vibration isolation mount. Furthermore, since a member which will be the base of the apparatus is necessary, with the exposure apparatus in the Japanese Patent Laid Open No. 02-199813, a main body mount which supports the main body holding the projection lens and a XY stage mount which supports the XY stage are arranged on the same positioning supporting bed. Therefore, even with the exposure apparatus described in the disclosure above, the vibration caused by the reaction force when the XY stage is driven travels via the XY stage mount to the positioning supporting bed, and the vibration further travels via the main body mount to the projection optical system held by the main body. This makes it obvious that the pattern image shift and the image blur and the like, described earlier, cannot be totally prevented.
Since the device rule will become finer in the future, and the wafer and the reticle larger in size, it is evident that the vibration caused when the stage is driven will become a more serious problem. Accordingly, the requirement of a new technology to be developed is pressing, to effectively suppress the adverse effects of the vibration of each component affecting the exposure accuracy.
The present invention has been made in consideration of the situation described above, and has as its first object to provide an exposure apparatus and exposure method which improves both the exposure accuracy and the throughput.
And the present invention has as its second object to provide a highly integrated device on which a fine pattern is accurately formed, and the device manufacturing method.
According to the first aspect of the present invention, there is provided a first exposure apparatus which forms a predetermined pattern on a substrate (W) by using an exposing optical system (PL), the exposure apparatus comprising: a main column (14) which supports the exposing optical system; a first vibration isolator (56A to 56C) which supports the main column; a first base member (BP1) which supports the first vibration isolator, mounted on the floor surface (FD); a stage supporting bed (16) which supports a substrate stage (WST) which holds the substrate; a second vibration isolator (66A to 66C) which supports the stage supporting bed; and a second base member (BP2) which supports the second vibration isolator, mounted on the floor surface independently from the first base member.
According to this aspect, the first vibration isolator supporting the main column is arranged on the first base member, and the second vibration isolator supporting the stage supporting bed is arranged on the second base member which is arranged on the floor surface independently from the first base member. Therefore, vibration travelling between the first base member and the second base member is nearly cut off. So, the reaction force caused with the movement (driving) of the substrate stage supported on the stage supporting bed travels to the second vibration isolator and the second base member, but does not travel to the first base member side. Thus, the reaction force caused with the movement (driving) of the substrate stage is not the cause of vibration of the exposing optical system supported by the main column. Accordingly, positional shift or unevenness in uniformity of line width of the pattern formed on the substrate due to the vibration of the exposing optical system can be effectively suppressed, and the substrate stage can have higher speed and larger size, which leads to an improvement in throughput.
In this case, as the vibration isolator, a passive vibration isolator which function is solely to isolate fine vibration from the floor surface may be used. It is, however, preferable to have at least one of the first vibration isolator and the second vibration isolator to be an active vibration isolator, which can positively control the vibration occurring to the main column or the stage supporting bed.
In this description, an active vibration isolator comprises an air mount which internal pressure is controllable, and an actuator such as a voice coil motor. And, it refers to a vibration isolator which has the function of removing vibration of the object subject to vibration control by controlling the voice coil motors and the like, based on the measurement values of the vibration sensors (such as accelerometers) attached to the object subject to vibration control.
With the first exposure apparatus according to the present invention, for example, in the case the first vibration isolator (56A to 56C) is an active vibration isolator, the exposure apparatus may further comprise: a column position measurement unit (98) which measures a positional relationship between the first base member (BP1) and the main column (14); and a controller (50) which controls the first vibration isolator based on a measurement value of the column position measurement unit. In such a case, the controller controls the first vibration isolator based on the positional relationship between the first base member and the main column measured by the column position measurement unit. And the main column, and naturally the exposing optical system supported by the main column, can be maintained at a stable position with the first base member as a datum. In addition, for example, in the case a mask stage which holds the mask is arranged on the main column, the vibration caused in the main column due to the movement of the mask stage can be suppressed or removed by the active vibration isolator supporting the main column.
In addition, with the first exposure apparatus according to the present invention, for example, in the case the second vibration isolator (66A to 66C) is an active vibration isolator, the exposure apparatus may further comprise: a stage supporting bed position measurement unit (94) which measures a positional relationship between the first base member (BP1) and the stage supporting bed (16); and a controller (50) which controls the second vibration isolator based on a measurement value of the stage supporting bed position measurement unit. In such a case, the controller controls the second vibration isolator based on the positional relationship between the first base member and the stage supporting bed measured by the stage supporting bed position measurement unit. Also, the vibration caused in the stage supporting bed due to the movement of the substrate stage can be suppressed or removed by the active vibration isolator.
With the first exposure apparatus according to the present invention, the exposure apparatus may further comprise a supporting member which supports the exposing optical system at three points by a V-groove, a conical groove, and a planar surface in respect to the main column. In such a case, the exposing optical system is supported in what is called a kinematic support via the supporting member in respect to the main column. Therefore, the expansion and contraction force, as well as the moment does not travel between the main column and the exposing optical system. Accordingly, the exposing optical system can easily be assembled into the main column, and furthermore, stress after assembly due to the vibration of the main column and the exposing optical system, change of temperature, and change of posture can be most effectively reduced.
With the first exposure apparatus according to the present invention, in the case the second vibration isolator is an active vibration isolator, the exposure apparatus may further comprise: a three degrees of freedom position measurement unit which optically measures a positional relationship between the exposing optical system and one of the stage supporting bed and the substrate stage in directions of three degrees of freedom, which are directions of an optical axis of the exposing optical system and a tilt direction in respect to a plane perpendicular to the optical axis; and a controller which controls the second vibration isolator based on a measurement value of the three degrees of freedom position measurement unit. In such a case, with the three degrees of freedom position measurement unit, the positional relationship between the exposing optical system and one of the stage supporting bed and the substrate stage is optically measured in directions of three degrees of freedom in the optical axis direction of the exposing optical system and a tilt direction in respect to a plane perpendicular to the optical axis. And the controller controls the second vibration isolator based on the measurement values of the three degrees of freedom position measurement unit. Thus, the positional relationship between the exposing optical system and the substrate stage is adjusted in directions of three degrees of freedom in the optical axis direction of the exposing optical system and a tilt direction in respect to a plane perpendicular to the optical axis. Accordingly, for example, even in the case where it is difficult to detect the position and posture of the surface of the substrate in directions of three degrees of freedom, the positional relationship between the exposing optical system and the substrate stage can be adjusted in directions of three degrees of freedom. That is, focus leveling control is possible, or the focus can be brought to a proximate level for focus leveling control.
In this case, the main column can have a supporting member which supports a barrel of the exposing optical system, and the three degrees of freedom position measurement unit can comprise: an interferometer which can measure the distance between one of the stage supporting bed and the substrate stage, and the supporting member at three different points. In this case, the interferometer may of course, be fixed to the supporting member, however, the interferometer may also be fixed to the barrel of the exposing optical system.
Alternatively, the three degrees of freedom position measurement unit may comprise: an interferometer which measures distance between one of the stage supporting bed and the substrate stage, and the exposing optical system at three different points.
With the first exposure apparatus according to the present invention, in the case the exposure apparatus further comprises a mask holding member (RST) which is supported by the main column (14) and holds a mask (R) on which the predetermined pattern projected on the substrate (W) by the exposing optical system (PL) is formed, at least one of a mask carriage system (110) which loads and unloads the mask in respect to the mask holding member and a substrate carriage system (112) which loads and unloads the substrate in respect to the substrate stage (WST) is arranged on the first base member (BP1), and the exposure apparatus can further comprise: a position measurement system (98) which measures a positional relationship between the first base member and the main column; an interferometer system (46, 90X, 90Y) which measures a position of at least one of the mask holding member and the substrate stage with one of the exposing optical system and a part of the main column as a datum; and a controller (50) which controls the carriage system arranged on the first base member based on a measurement value of the position measurement system and the interferometer system. With this arrangement, for example in the case the interferometer system measures the position of the mask holding member with the exposing optical system (or a part of the main column) as a datum, the controller can for example, control the mask carriage system based on the measurement values of the interferometer system and the position measurement system when the mask is exchanged. By doing so, the position of the mask holding member which datum is the first base member during carriage, can be fixed at all times, and as a consequence, the mask can be loaded on the mask holding member at the desired position.
In addition, in the case the interferometer system measures the position of the substrate stage with the exposing optical system (or a part of the main column) as a datum, the controller can for example, control the substrate carriage system based on the measurement values of the interferometer system and the position measurement system when the substrate is exchanged. By doing so, the position of the substrate stage which datum is the first base member can be fixed at all times, and as a consequence, the substrate can be loaded onto the substrate stage at the desired position.
With the first exposure apparatus according to the present invention, in the case the exposure apparatus further comprises an illumination optical system (ILU) which illuminates the mask, the illumination optical system may be arranged on a third base member (BP3) which is arranged on the floor surface independently from the first base member and the second base member. In such a case, vibration can be kept from travelling between the objects respectively arranged on the first, second, and third base member.
With the first exposure apparatus according to the present invention, the first vibration isolator (56A to 56C) may be an active vibration isolator, and the exposure apparatus may further comprise: a mask holding member (RST) which holds a mask (R) on which the predetermined pattern is formed, and finely drives the mask on a surface of the mask above the main column (14) in directions of three degrees of freedom; an illumination optical system (ILU) which illuminates the mask; an active vibration isolator (116) which supports the illumination optical system; a six degrees of freedom position measurement unit (120) which measures a positional relationship between the illumination optical system and the main column in directions of six degrees of freedom; a controller (50) which controls the mask holding member and one of the first vibration isolator and the active vibration isolator holding the illumination optical system, based on a measurement value of the six degrees of freedom position measurement unit. In such a case, the controller adjusts the mask via the mask holding member within the surface in directions of three degrees of freedom based on the positional relationship between illumination optical system and the main column obtained based on the measurement values of the six degrees of freedom position measurement unit. The controller also controls the active vibration isolator holding the first vibration isolator or the illumination optical system, and can adjust the positional relationship between the illumination optical system and the mask in directions of six degrees of freedom.
With the first exposure apparatus according to the present invention, the mask may be movable in a predetermined direction with predetermined strokes within a surface which is perpendicular to an optical axis of the exposing optical system, and the exposure apparatus may further comprise a driver (44, 50, 72) which synchronously drives the mask and the substrate stage in the predetermined direction. In such a case, the driver drives the mask and substrate stage in synchronous within a plane perpendicular to the optical axis of the exposing optical system, and by what is called scanning exposure, the pattern of the mask is accurately transferred onto the substrate with the exposing optical system.
According to the second aspect of the present invention, there is provided a second exposure apparatus which forms a predetermined pattern on a substrate by using an exposing optical system, the exposure apparatus comprising: a main column which supports the exposing optical system; a substrate stage which holds the substrate and is supported independently from the main column; a focus detector (121a, 121b) which detects a position of a surface of the substrate in at least a direction of an optical axis of the exposing optical system; a substrate driving system (88) which drives the substrate in the direction of the optical axis of the exposing optical system; a position measurement system (94, 98, 102) which is arranged independently from the focus detector, and measures a positional relationship between the exposing optical system and the substrate stage; a driver (70) which changes the positional relationship between the exposing optical system and the substrate stage; and a controller (50) which is connected to the focus detector, the substrate driving system, the position measurement system, and the driver, wherein the controller controls the driver and sets the exposing optical system and the substrate stage in a predetermined relationship based on a value measured by the position measurement system, and adjusts a positional relationship between an image plane of the exposing optical system and the substrate via the substrate driving system based on a detection result of the focus detector.
In the case the main column supporting the exposing optical system and the substrate stage holding the substrate is supported individually, although there is an advantage of vibration being difficult to travel between the main column and the substrate stage, there is a risk of the two making individual movements. This may cause a response delay (time delay) in the focus control of the substrate during exposure or the focus leveling control.
However, according to the present invention, on exposure, the controller controls the driver based on the values measured by the position measurement system, in other words, the measurement result of the positional relationship between the exposing optical system and the substrate stage, and the positional relationship between the exposing optical system and the substrate stage is set at a predetermined relationship. Also, the controller adjusts the positional relationship between the image plane of the exposing optical system and the substrate via the substrate driver, based on the detection results of the focus detector. That is, the positional relationship between the exposing optical system and the substrate stage is set at a predetermined relationship, before the controller starts the focus control or focus leveling control on the substrate based on the detection results of the focus detector. Therefore, this can prevent the response delay from occurring when focus control or focus leveling control is performed on the substrate, resulting in a more precise focus control or focus leveling control, allowing improvement in exposure control. In this case, again, with the same reasons as of the first exposure apparatus described earlier, the substrate stage can have higher speed and larger size, which allows an improvement in throughput.
The predetermined relationship, referred to above, is a positional relationship, for example, when considering the responsiveness of the substrate driving system, the surface of the substrate is positioned within a range where pre-exposing dynamic focusing can be sufficiently performed and no delay occurs in the focus control. That is, a positional relationship where the surface of the substrate is positioned in the vicinity of the focal position of the exposing optical system and can be detected at all times with the focus detector.
The substrate driving system, may be arranged on the substrate stage and a system which drives the substrate in at least the optical axis direction of the exposing optical system. Or, it may be a system which drives the substrate in at least the optical axis direction of the exposing optical system via the substrate stage.
Furthermore, with the present invention, since the focus control or focus leveling control on the substrate can be performed based on the detection results of the position measurement system, in the case of performing exposure on a dummy shot where detection by the focus detector is difficult or when performing exposure on an inward shot and an edge shot, focus control or focus leveling control on the substrate becomes possible. And as a consequence, allows improvement in controllability of the line width.
With the second exposure apparatus according to the present invention, the position measurement system may measure the positional relationship in directions of three degrees of freedom, in an optical axis direction of the exposing optical system and a tilt direction in respect to a plane perpendicular to the optical axis.
In this case, the position measurement system may be fixed to the main column supporting the exposing optical system, or, the position measurement system may be fixed to the barrel of the exposing optical system.
With the second exposure apparatus according to the present invention, in the case the exposure apparatus further comprises a stage supporting member which supports the substrate stage, the position measurement system can measure a positional relationship between the exposing optical system and the stage supporting member in an optical axis direction of the exposing optical system. In such a case, the position measurement system measures the positional relationship between the exposing optical system and the stage supporting member in the optical axis direction of the exposing optical system. Therefore, consequently, this means that the positional relationship between the exposing optical system and the substrate stage supported by the stage supporting member is measured in the optical axis direction of the exposing optical system.
In this case, three measurement points may be arranged on the stage supporting member to measure the positional relationship, and the position measurement system may measure the distance between the exposing optical system and the stage supporting member at the three measurement points. In such a case, based on the measurement results of the distance at the three points, the positional relationship between the exposing optical system and the stage supporting member, in other words, the positional relationship between the exposing optical system and the substrate stage can be obtained in directions of three degrees of freedom in the optical axis direction of the exposing optical system and a tilt direction in respect to a plane perpendicular to the optical axis.
With the second exposure apparatus according to the present invention, the exposure apparatus may further comprise a base member (BP1) which supports the main column, and the position measurement system may have a first position measurement unit (98) which measures a positional relationship between the base member and the exposing optical system, and a second position measurement unit (94) which measures a positional relationship between the base member and the stage supporting member. In such a case, the first position measurement unit measures the positional relationship between the base member and the exposing optical system, and the second position measurement unit measures the positional relationship between the base member and the stage supporting member. Therefore, based on the measurement results of the first position measurement unit and the second position measurement unit, the positional relationship between the exposing optical system and the stage supporting member, in other words, the positional relationship between the exposing optical system and the substrate stage can be obtained.
In this case, at least one of the first position measurement system and the second position measurement system may obtain a relative position in directions of six degrees of freedom as the positional relationship.
According to the third aspect of the present invention, there is provided an exposure method to form a predetermined pattern, by using an exposing optical system, on a substrate on a substrate stage, which is supported independently from a main column supporting the exposing optical system, the exposure method comprising: a first step of measuring a positional relationship between the exposing optical system and the substrate stage; a second step of setting the positional relationship between the exposing optical system and the substrate stage to a predetermined state, based on values measured in the first step; and a third step of forming the pattern onto the substrate in a state of the predetermined state set in the second step, while adjusting a positional relationship between an image plane of the exposing optical system and a surface of the substrate based on a detection result of a position of the surface of the substrate in at least an optical axis direction of the exposing optical system.
As is described earlier, in the case the main column supporting the exposing optical system and the substrate stage holding the substrate is supported individually, although there is an advantage of vibration being difficult to travel between the main column and the substrate stage, there is a risk of the two making individual movements. This may cause a response delay (time delay) in the focus control of the substrate during exposure or the focus leveling control.
However, with the present invention, in the first step the positional relationship between the exposing optical system and the substrate stage is measured, and in the second step, based on the values measured, that is, the measurement result of the positional relationship between the exposing optical system and the substrate stage, the positional relationship between the exposing optical system and the substrate stage is set at a predetermined state. And in the third step, with the positional relationship set at the predetermined state, the relative position between the image plane of the exposing optical system and the surface of the substrate is adjusted based on the detection result of the position of the substrate surface at least in the optical axis direction of the exposing optical system, and the pattern is formed on the substrate.
Accordingly, in the second step, the positional relationship between the exposing optical system and the substrate stage is set at a predetermined relationship based on the measurement results in the first step, before the controller starts the focus control or focus leveling control on the substrate based on the detection results of the focus detector in the third step. Therefore, this can prevent the response delay from occurring when focus control or focus leveling control is performed on the substrate, resulting in a more precise focus control or focus leveling control, allowing improvement in exposure control.
The predetermined relationship, referred to above, is a positional relationship, for example, when considering the responsiveness of the substrate driving system, the surface of the substrate is positioned within a range where pre-exposing dynamic focusing can be sufficiently performed and no delay occurs in the focus control. That is, a positional relationship where the surface of the substrate is positioned in the vicinity of the focal position of the exposing optical system and can be detected at all times with the focus detector. In this case, again, with the same reasons previously, the substrate stage can have higher speed and larger size, which allows an improvement in throughput.
In this case, in the first step, the positional relationship may be measured in directions of three degrees of freedom, in an optical axis direction of the exposing optical system and a tilt direction in respect to a plane perpendicular to the optical axis.
With the exposure method according to the present invention, in the first step, the measurement may be performed by using a position measurement system fixed to the main column supporting the exposing optical system. Or, in the first step, measuring the positional relationship may be performed by using a position measurement system fixed to the barrel of the exposing optical system.
With the exposure method according to the present invention, in the case the substrate stage is supported by a stage supporting member, in the first step, a positional relationship between the exposing optical system and the stage supporting member may be measured in an optical axis direction of the optical system. In such a case, in the first step, the positional relationship between the exposing optical system and the stage supporting member is measured in the optical axis direction of the exposing optical system. And as a consequence, this means that the positional relationship between the exposing optical system and the substrate stage which is supported by the stage supporting member is measured in the optical axis direction of the exposing optical system.
In this case, in the first step, distance between the exposing optical system and the stage supporting member may be measured at three different measurement points arranged on the stage supporting member. In such a case, based on the measurement results of the distance at the three points, the positional relationship between the exposing optical system and the stage supporting member, in other words, the positional relationship between the exposing optical system and the substrate stage can be obtained in directions of three degrees of freedom in the optical axis direction of the exposing optical system and a tilt direction in respect to a plane perpendicular to the optical axis.
With the exposure method according to the present invention, in the case the main column is supported by a base member, the first step can include a first measurement step of measuring a positional relationship between the base member and the exposing optical system, and a second measurement step of measuring a positional relationship between the base member and the stage supporting member. In such a case, in the first measurement step, the positional relationship between the base member and the exposing optical system is measured, and in the second measurement step, the positional relationship between the base member and the stage supporting member is measured. And as a consequence, based on the measurement results of the first measurement step and the second measurement step, the positional relationship between the exposing optical system and the stage supporting member, in other words, the positional relationship between the exposing optical system and the substrate stage can be obtained.
In this case, in at least one of the first measurement step and the second measurement step, a relative position in directions of six degrees of freedom may be obtained as the positional relationship.
In addition, in a lithographic process, by using the exposure method according to the present invention, a multiple layer of patterns can be formed on a substrate with high overlay accuracy, allowing microdevices with higher integration to be produced with high yield, improving its productivity. Likewise, in the lithographic process, by using the exposure apparatus according to the present invention, a multiple layer of patterns can be formed on the substrate with high overlay accuracy. Accordingly, this allows microdevices with higher integration to be produced with high yield, which leads to an improvement in productivity. Therefore, from another aspect of the present invention, there is provided a device manufacturing method that uses the exposure apparatus of the present invention, and a device manufactured by the device manufacturing method.